My ex and I were together 10 years, 8 years were like one long honeymoon then the last two were progressive abuse and violence. It doesn't get better it gets worse.

You need to find a support network. There are places for abused spouses. Yes even men living with domestic abuse, which is what this is by the way, don't kid yourself it's anything else.
You need to break the silence,it's giving her power. I don't mean the silent treatment I mean the hiding it from anyone else.
Record the incidents, encourage your daughter to report to the schools guidance counsellor. Don't make her keep this secret.
You say your wife can turn on the nice switch, but she can't keep it up. Can you record these attacks. Nanny cams are a blessing in these situations.
Is there no family your daughter could stay with just now.
I take it the older daughter won't vouch for you if you reported her?

I reiterate, find a support group for spouses at risk of domestic abuse. It's the beginning of the support you need to get out if you can't do it alone.

Please don't wait til it's too late.